


VASSAL

by lunaryu (zeroshikidarkangel)



Category: Black Clover - Tabata Yuki (Anime & Manga)
Genre: Demons, Drama, Fluff, Foul Language, M/M, Purple Prose, Reincarnation, Romance, Shounen-ai, Slight OOC, sequence of short scenes, spoilers (for anime fans-only)
Language: English
Status: Completed
Published: 2019-12-05
Updated: 2019-12-05
Packaged: 2021-02-18 16:23:18
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings, No Archive Warnings Apply
Chapters: 1
Words: 7,949
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21680263
Author URL: https://archiveofourown.org/users/zeroshikidarkangel/pseuds/lunaryu
Summary: It's not a coincidence that the Five-leafed CloverGrimoirepicks Asta as its Master. The soul of an elf, the one that's turned into a demon, has been watching over him since the first time Asta has awakened him. Asta only has to say yes, and he can obtain Licth's power, in exchange of housing his demonic soul.Too bad Asta is so stubborn, and worse, the incarnation of Licth's wife is holding Asta's humanity so strongly…
Relationships: Asta/Yuno (Black Clover), Licht/Asta (one-sided)
Comments: 9
Kudos: 303





	VASSAL

**Author's Note:**

> Yah, meet me again, friends. This is my second attempt at making a (hopefully) decent fan fic for this fandom. Just pray that it doesn't turn out too bad. So, a little bit of rare pairing (Licht/Asta) on the side, relationship-wise, but still heavily in Yuno/Asta persuasion at the end. Enjoy.
> 
> **Disclaimer: Black Clover © Tabata Yuuki**
> 
> **Warning:** _light shounen ai, purple prose (?), heavy spoiler for anime-fan only (but with any luck, it's vague enough), foul language, sequence of short scenes, fluff, probably slightly oOC, and possible grammar and spelling errors, etc…_

**VASSAL**

**© ~lunaryu**

* * *

The first time Asta met the _spirit_ , he was 10 years old.

Asta was playing in the forest, just below the skull of the Demon that nearly destroyed human race hundreds years ago. For some reason, since he had heard the story that Sister Lily told him and Yuno, about Wizard King that defeated the Three Eyed Demon, Asta felt this pull to investigate the remains of the Demon, seeking more proofs that the Wizard King and the Demon really did exist in this world.

Alright, maybe not _exactly_ to investigate since it was unnecessary. Sister Lily already told Asta and Yuno that the Wizard King did exist and the skull was enough proof that the Demon also existed. In that quiet and deserted part of the forest, Asta could practice and train his body to become stronger, so when his magic finally awakened, he would be more prepared, especially to control it. True, right now he was a bit behind, since Yuno already got his wind magic, but it didn't mean he had lost from his rival. He would get his magic eventually. In the meantime, training to improve his physical fitness and strength could be very useful.

Asta was jogging deep into the forest when he stumbled into a weird looking rock. It was embedded in the soiled ground deeply, its shape reminding Asta of a tree, actually, just the root parts, twisting and twining around some unidentifiable shape in the middle.

_Is that supposed to be a flower?_

Curious, Asta approached it. It was definitely made of rock, though, because when he touched it, the mass was hard and didn't give under pressure. The _flower_ shape was nothing like Asta had ever seen before. The petals were huge and despite the root-like rock surrounding and looping around it, the pistil and the stamens were still visible, if those parts were really pistil and stamens.

Though, the shape of the pistil was a bit weird. The 'head' of the pistil had part that looked like pigtail. Asta tilted his head aside slightly, bemused. The stamens were in pair, one on each side of the pistil, shaped like arms.

Filled with inquisitiveness of a child, Asta reached out to touch the pistil, but his hand had to pass through some of the root-like rocks and there was sharp part of the rock that accidentally cut his skin. Asta winced and grimaced slightly at the sting and the cut seemed to be deep enough because some of his blood dripped from the open wound to the pistil. He hurriedly pulled his hand back, inspecting the damage while whining slightly.

Sister Lily would lecture him for sure, for not being careful enough. Asta pouted at the thought and was about to turn to leave, but then immediately paused as he caught a slight movement from the rock in his peripheral vision.

Asta turned to face the rock once more. Tilting his head aside, he noticed that something resembling of smoke began to appear around the pistil and the stamens. It was dark and swaying, moving around like fire, and before Asta could look more closely, it suddenly surged out wildly. Like a broken dam, the dark thing began to fill the space around it with dark smog, even Asta got swallowed by it that he had to close his eyes and protect his face from the surge with both arms.

A few seconds later, the surge seemed to recede and start to settle. Asta slowly uncovered his face from his crossing arms. Upon realizing that his surrounding had become so dark and he could hardly see anything, Asta began to feel anxious.

_What's going on here?_

There was a rustling sound in front of Asta and he jolted in surprise and alarm.

_What was that just now?_

"Who is there?!" Asta asked rather loudly, his heart beginning to pound a tad harder and faster.

There was a growling sound now and Asta began to fear that it was a wild beast or something. He gulped and took a few steps back. He didn't bring any weapon to defend himself. If it was really a carnivore, Asta had to run before it attacked him.

Asta took another step back and narrowed his eyes to try to see more clearly among thick dark smog. He had to know where the position of the wild beast if he wanted to successfully run away. Asta sharpened his eyesight and hearing, and a few seconds later something moved to 'reach' him from inside the smog. Five very long black claws appeared and Asta jumped back in reflex before the claws could touch him, while large dark humanoid black mass began to appear, eyes as red as pools of blood and everything of its parts screamed 'danger'.

Asta squeaked in horror and didn't hesitate to run away screaming, away, _away_ from the dark entity that definitely wanted to harm him.

Asta ran and ran and kept running. He didn't dare to look back.

* * *

The second time Asta encountered the _spirit_ was a few days after he met them the first time, even though at the time he hadn't known that they were the same entity.

Asta had come back to the forest clearing bellow the Demon's skull.

He couldn't believe that he had run away screaming the last time he had been there, his _training_ place. He meant, he was probably just exhausted or something. There was no such thing as… as _ghost_ , after all. He hadn't told a soul about his encounter with the dark entity in the forest. He didn't want Sister Lily, moreover, _Yuno_ to know that he had run away because he was _afraid_. Asta was _not_ a scaredy-cat. He was not a coward either. He had to make sure that the dark entity he had encountered was just a figment of his over-imagination. So, Asta decided that he would face down his fear and come back to the place, to settle it once and for all.

Asta hid part of his body behind a dead tree. He peeked into the clearing just around the strange rock he had poked around before. Luckily, it was still day-time, so a lot of patches on the ground got sunlight that trespassed some fissures of the skull. Asta blinked once and twice, making sure that no one… no entity was around.

 _See? It's just my over-imagination after all!_ —he sighed in relief as the thought crossed his immature mind.

Asta came out from his hiding spot and walked into the clearing tentatively. Nothing happened. He nodded to himself and approached the strange flower-like rock again, intending to follow up his initial investigation from a few days prior.

_There is nothing to be afraid of. It's perfectly safe. I've been playing around this place for years, since I heard the story of the Wizard-King and the Three Eyed Demon. Nothing major happened before, so… it's alright._

Asta convinced himself as he looked more closely to the weird shaped rock. Before, he was overly on edge because it had been his first time venturing so deeply into the forest. This time he was more prepared. He would be okay.

"As I thought, the flower shape is also strange," Asta tilted his head aside slightly, his curiosity prominent once more. Of course the root-like shape rocks was also strange. It seemed that those roots were there to 'restrain' the flower, and after looking at the 'pistil' more closely, Asta could pick up peculiar shape on it, like… _engraving_?

Staring at them for a long time, Asta thought that the shape of the engraving was familiar, somehow… They almost looked like…

"Parts of human face?" Asta tilted his head to the other side, frowning. "That can't be… right?"

**" _Oi, brat."_**

Asta shrieked instantly, shocked and jumped almost a meter into the air at the sudden heavy, croaky voice.

"W-w-w-w-who is it?!" Asta looked around in panicky, drawing up a sharpened stick in front of him with both trembling hands, his hearts beating a mile per minute, trying to locate the owner of the voice.

There was silence for a moment before a growling sound was heard from behind Asta and he whirled to hit whatever it was that was making such horrid sound, but there was nothing behind him, just encompassing darkness that came from the thick forest around the clearing.

"Show yourself!" Asta shouted loudly, hands still shaking badly, but he gripped his stick more tightly in an attempt to steady them.

A dark chuckle was heard from his side and Asta turned to face whatever it was that made such condescending voice. **_"You think that stick can protect you from me?"_**

"Who are you?! Show yourself! I'm not afraid of you!" Asta yelled once more, more confidence and bravery inserted in his tone. He wouldn't be defeated by his fear. He could conquer it!

 **" _Oh, but you should be, kid…"_** the voice was getting lower, another growl featuring the end of their sentence.

"I am not _kid_! I'm Asta! Asta from Hage Village!" Asta shouted again, not even thinking much as he introduced himself to the entity or creature or whatever it was. "Come out here and show yourself!" he called out again and there was an eerie pause in the air before-

 **" _Did you just introduce yourself to me?"_** The entity asked which such incredulous tone that Asta was taken aback.

"W-what of it? It's only polite to mention your name first before you ask for others!" Asta made excuse. It was the thing that was taught relentlessly by Sister Lily and Father Orsi since he and Yuno started to understand words. It stuck, alright.

There was another pregnant silence before- **_"Pft—ahahahahaha!"_** the entity suddenly started laughing. The peal of laughter sounded weird, coming out high, like bursting and ringing, echoing around the forest at the same time.

Asta was befuddled once more, not expecting laughter as a response of his introduction. Beads of sweat rolled down his cheek one by one as he kept hearing the laughter and he didn't know how he should react to it aside scowling. "What's so funny!?" he shouted again, a bit annoyed.

 **" _No, well…"_** there was another weird sound, like they almost _giggled_ , before they continued laughing as they spoke. **_"It's been awhile since I met such a polite, funny kid."_**

Asta bristled again for being called a kid once more, but before he could protest, the entity added. **_"Such a weird child… Do your parents not teach you to not give your name to a stranger, kid?"_**

"I have no parent. I'm from the orphanage at the church," Asta said casually, but still drawing up his stick strongly, as if he could almost hear the pause of the entity's train of thought. "But Father Orsi is practically my dad and Sister Lily is practically my mom, my sister, and my future wife!" he added the last part proudly.

…

 **" _You can't marry a woman of the cloth, kid,"_** the entity reproached dryly.

"I'm not giving up on her no matter what other people said!" Asta reverted to his default argument then and the entity chuckled in reaction. It was kind of odd that they only commented on the last part of Asta's words. People usually mocked him for being an orphan and yet the demon _ignored_ that fact at all.

It was as if… there was nothing _wrong_ with Asta being an orphan.

**" _You're such an odd kid."_**

"Hey! I told you! I'm not a kid! I'm Asta!" Asta argued again more stubbornly. "And show yourself already! It's not fair if I can't see you!"

**" _What are you talking about, little one? You'd been staring uncomfortably closely at my face just moments ago."_**

The entity's voice sounded _deadpanned_. How come Asta could know that was beyond him. But as he heard them, Asta blinked once, dumbfounded. "Eh?"

Asta then turned his body to look at the weirdly shaped 'flower' that was bound by root-shaped rock. He stared at the pistil engraving for a long time before he realized it. "You're that _flower_?!"

Asta dropped his jaw.

 **" _Wait, you just realized it?"_** Even the entity sounded nonplussed.

Yeah, that was shocking indeed.

* * *

Asta didn't make a habit to go to the forest just to talk to the entity.

Nope. Not at all.

Asta only came back to the clearing to _train_ his body. The entity talking to him and giving occasional advice was just an extra.

**" _You're indeed a weird kid. You really aren't afraid of me now, despite running like a bat out of hell the first time you saw me."_**

Asta was doing push up as the entity started talking and he just shrugged. "You're a talking _flower_ , no big deal. I can accept the fact despite how weird it is."

 **" _I'm not a flower,"_** the entity made a long suffering sigh. **_"I told you I am a 'demon'. Although I'm restraint at this moment and only my voice can reach your world, I'm still a very scary being, you know."_**

Asta stopped his push up and exhaled deeply as he reached fifty counts and then changed his position to do some sit up this time, while thinking of how to respond to that information. True, the entity had told Asta that _he_ was a demon. But he never showed his true 'form' to Asta except for that first time when he saw him a few months back, part of him, at least. Those big sharp claws that tried to reach Asta, that was the _demon_ form, only smaller and weaker, since he had apparently been asleep for centuries.

 **" _Your blood woke me,"_** the entity said, his voice sounding amused. **_"Human blood is indeed the best to restore my power."_**

"I'm not going to give you more of my blood, you know," Asta had retorted then, suddenly feeling cautious if the demon would start targeting his blood after that.

 **" _What a shame. I can lend you my power if you set me free."_** There was a mirth in the demon's tone, as if he knew exactly what was bothering Asta all his life.

Asta flinched and stopped his sit-up at the count of fifteenth. He turned to face the rock and narrowed his eyes at it. "You can give me 'magic'?" he asked, completely skeptical.

 **" _Demon power isn't exactly 'magic',"_** the demon said almost languidly, not even trying to lie to Asta about how his power worked.

"Yeah… it's more like a 'curse' right?" Asta huffed. "I read about it," he continued, remembering his research about demons lore in the holy book in the church just after the demon told Asta of his origin. "What kind of demon are you?"

It was part curiosity and part fear. Asta wanted to know about the demon more because he wanted to find a way to cast him back to where he belonged.

All demon belonged in the underworld after all.

 **" _Unfortunately,"_** the demon whispered. **_"I don't remember."_**

* * *

It was not a lie.

He didn't remember what kind of demon he was. There were bits and pieces of his memory before he went to sleep. No, before he _was_ _made_ to sleep _._

He remembered hatred.

He remembered pain.

He remembered despair.

He remembered rage.

He remembered devastation.

He remembered a face. Child-like, youthful, a beautiful cheery smile, pools of aquamarine in their eyes, sunlight in their hair.

" _Licht."_

A clear tenor voice calling _his_ name.

The demon remembered his previous name _before_ he was a demon, but he didn't remember his demon name.

* * *

"It's difficult to refer you if you don't have a name," Asta grumbled, three months after he discovered the demon's 'sleeping' place.

The demon wasn't corporeal. He didn't know what the demon had done, but Asta could make out his 'form' as a shadow now, sometimes attached to his restraint body, a.k.a. the 'flower', sometimes detached from it, lurking behind the shadows of trees and rocks. He even attached himself to Asta's shadow once or twice.

It was undoubtly creepy when you could make out bloody red eyes from your own shadow, but Asta took it in stride because he didn't actually feel any malice from him. The demon even asked for permission before he attached himself to Asta's shadow. Wasn't he a polite demon?

"What do you want to be called?" Asta asked as he jogged around the clearing for a pre session of his training. Today he wanted to clear 75 counts of push-up and 75 counts of sit-up. Before long he would clear 100 counts.

 **" _Whatever you want to call me, kid. I don't really give a damn,"_** the demon answered, sounding bored out of his mind.

"You said a bad word again," Asta huffed after cringing. He shuddered at the thought of Sister Lily using her Aqua Magic to cleanse the children's mouths after they said bad words as a punishment. Asta learned a hard lesson to _not_ repeat those bad words just because the adults did it in regular basis.

**" _Demon, remember?"_**

Asta could almost see the demon haughtily raising one of his eyebrows. He sighed, sweat dropping. "Well… I guess I'll pick a name for you, then," he mumbled, tilting his head to right and to left alternatively as he contemplated. "Hm…"

Asta looked around to the clearing, noticing patches of sunlight on the ground, some even falling on the 'flower', almost illuminating the pistil and stamens into gold.

_Golden light…_

"Rihito."

There was a strange shiver that swept down the entire clearing as Asta said the name. Goosebumps rose on Asta's skin so suddenly that he had to stroke his arms and neck once or twice. The demon was suspiciously quiet.

"You don't like it?" Asta asked after a full minute of total silence.

 **" _Call me whatever you like."_** The Demon, Rihito, repeated his words a few moments ago, and Asta nodded.

"Rihito it is."

* * *

**" _Why Rihito?"_**

The demon asked in their nth meeting. He didn't count how many times he had met the demon at this point, but it had been two years after their first meeting. Asta was twelve now, and as before, he hadn't gotten any magic this year either.

"What?" Asta turned to the almost corporeal shadow now. Rihito had been walking around in a specific form, a step ahead of a shadow that had real mass, shape, and wasn't attached to any other shadow. Asta could even make out his face now, only… still in black color and blood-red eyes, no sclera yet.

Just a black mass with red eyes.

_Creepy._

**" _Why Rihito?"_** the black mass repeated, sounding curious. **_"Don't you think it's weird you name a demon 'light'?"_**

Asta blinked once and twice before he continued his regimen. It was push up with one hand now. He needed to clear 300 today.

"You do realize I just gave you a name so it would be easier to refer you, right? I didn't think much at the time. I just looked around and saw those patches of sunlight on the soil and some fell on your 'flower'." Asta shrugged, remembering why he thought it was a good idea to name a demon 'light'. It just… fit, somehow. Those patches of sunlight were pretty and he wanted to call the demon with a pretty name.

There was silence after that. The demon just stared unredably at Asta while he was training and it wasn't uncomfortable or anything. Rihito just looked a bit skeptical as he finally said, _"I see."_

Then Rihito proceeded to comment that Asta's body position was faulty and he would injure his muscles if he kept moving that way.

* * *

The black mass took a humanoid shape.

Asta gaped slightly in bewilderment when the tall dark humanoid shape sat down on the bound 'flower' shaped rock, now looking more like a self-made throne rather than his real body.

"You can look like that now, huh?" Asta commented, still staring, almost able to make the shape of the demon's mouth. He was smirking, sharp saw-like shape ( _teeth?_ ) adorning his dark face.

 **" _Isn't it neat?"_** the demon chuckled, his blood-red eyes glinting, something beating behind his dark body, _flapping_.

"You have wings?" Asta narrowed his eyes at the black fluttering thing accusingly.

 **" _Of course I do. I'm a demon."_** His smirk got wider if it was possible. **_"You, on the other hand… haven't changed at all. Still short and magic-less."_**

"Shut up," Asta scowled at him. It was such a sore subject for Asta right then. He was turning fourteen this year and yet his magic had still eluded him. "I'm just a late bloomer," he huffed, pouting slightly.

The demon laughed then, mockingly as always, but it wasn't an evil laugh.

"You can laugh whatever you want, Rihito. I'm not about to give up!"

Right, Asta wasn't giving up hope yet. How could he, when he had ambition to become the Wizard-King. His magic would come to him eventually. He was sure of it. Besides, he had been drinking Moguro-leaf juice since he was turning thirteen. It had been said that essence of Moguro-leaf could increase magical power. He _would_ get his magic. He just needed to train his body some more.

Asta nodded and started his training again. He had passed through 700 counts for his push-up and sit up, and he would reached 1000 before he was fifteen. He already could do push up with one finger down, now, with all his body up in the air. He would get stronger.

 **" _Shouldn't you realize it by now that you're in denial, kid?"_** the demon taunted, not unkindly, just informatively. **_"I've been watching you for years since you woke me up, you know. Not once in those years I feel the magical seed inside you."_**

It was the brutal honesty that always got into Asta's head. Rihito never lied. Even though he was a demon, he hadn't told a single lie since he spoke to Asta.

"It doesn't matter," Asta replied, pacing his breath as he did one-finger push up, counting inside his head as he continued. "When I get my _Grimoire_ , my magic will reveal itself."

 **" _Everything will be so much easier if you just say yes to my offer."_** Rihito smirked. **_"I'll give you power beyond compare if you just accept me into your body."_**

Asta sent the demon a stink eye. "The way you talk such misleadingly will give people the wrong impression, you know?" He complained aridly and upon catching the innuendo in his own words, the demon laughed again.

 **" _You're as interesting as usual, Asta,"_** Rihito sounded much more amused now and Asta felt an odd sensation, like _personal accomplishment_ , whenever he heard the entertained laugh.

* * *

Rihito rarely laughed. He was hard to read and his words were usually detached of emotion even as he talked to Asta. He was sometimes quiet as well, just watching and listening to Asta talk without giving any comment, but he was _present_ and Asta could never ignore him since he was always around when he was in the clearing.

So Asta talked. He talked about his day, his chores and his education, telling stories about his chosen family, how he met them for the first time in the orphanage. He talked about Father Orsi, Sister Lily, about how nice and kind they were as a person, how the _loved_ Asta and the other kids with all of their hearts. He talked about Recca, Nash, Aruru and Hollo, his precious little brothers and sisters.

Asta talked about Yuno. About his promise to his _other half_ , his best friend and brother, his _rival_.

Rihito always showed peculiar interest whenever Asta spoke of Yuno's name.

When Asta pointed it out and asked why the demon was interested, the demon just gave him a smirk.

**" _I'm just interested because you show a different 'feeling' whenever you mention the brat."_**

Asta always yelled at Rihito afterward that Yuno wasn't a brat. He was a handsome jerk that drove Asta up the wall all the time and he was a _precious_ rival for him to become a Wizard King.

* * *

There were times when these 'human-meet-demon' occasions were interrupted by Yuno.

Yuno was sent to look for Asta whenever he got caught up in his training and forgot the time. If he wasn't back to the orphanage until dinner time, Sister Lily always asked Yuno to pick Asta up.

These intermissions weren't often, so Asta didn't bother to put his guard up.

Of course Asta hadn't told anyone about his _odd_ friend, Rihito. And yes, Asta considered the demon as his friend. Rihito hadn't done anything to earn him any distrust from Asta after all. He being a demon had nothing to do with him as a 'person'. Besides, Rihito didn't really remember his identity as a demon. Sure, he did all the offers to make a pact so he could possess living body, but it was just a job for him. Asta got a feeling that Rihito wasn't serious with his offer anyway. He just did it for principle, because he was a demon.

"Whom are you talking to, Asta?"

Asta jumped and shrieked in shock at the sudden voice from behind him. He immediately whirled and shouted loudly upon recognizing the voice. "Sheesh! Don't scare me like that, Yuno! You almost gave me a heart attack!"

Yuno just stared at Asta with raised eyebrows. "It's dinner time, Asta," he reminded and Asta was surprised that it had been dark outside the clearing.

"Oops," Asta chuckled sheepishly. "Sorry about that, getting caught up in training as usual," he scratched his cheek before turning to collect his training tools.

Yuno was silent as he waited for Asta. He looked around and made a thoughtful expression. "Did you train with someone here?" he asked slowly and Asta looked upward at Yuno, puzzled.

"No? You know nobody at the village can teach to save their lives," Asta chuckled, full of humor. "Besides, there's nothing they can teach if the student hasn't gotten his magic yet, right?"

"Hmm…" Yuno made another sweep of his golden eyes on their surroundings. "It sounded a lot like you were talking to someone earlier." He seemed mystified.

A bead of sweat dropped from Asta's cheek. He didn't used to keep secret from Yuno, or from anyone for that matter. He wondered if he could just tell the truth then. Would Yuno believe him that he was talking to a demon?

Asta glanced subtly behind him. The demon was still there, smirking. It was just that… the demon wasn't visible to any other person beside Asta. People tended to feel Rihito's presence as 'evil' and they were afraid of it, so they never made any effort to understand why they felt that way. Rihito had never been hiding his presence. He was simply _invisible_ to the naked eyes.

For some reason, it didn't apply to Asta though, because he was the one that woke the demon up from his slumber.

Asta switched his gaze to Yuno who was still looking around. Yuno must have felt the 'presence' too, which was why he seemed confused now, because he couldn't find the 'presence' with his eyes.

"I-it's probably just your over-imagination," Asta tried, smiling while sweating profoundly behind his neck. "Let's just go home!" He clapped Yuno's shoulder and steered him away from the clearing, away from the still smirking demon and his throne.

* * *

That kid… _Yuno_.

He felt a familiar presence inside his _soul_.

" _Licth."_

The demon closed his eyes, willing his faulty memory to remember the time before he became a demon.

" _Licth."_

A pair of sparkling green eyes, a soft smile, pretty flowers in her wavy golden-blond hair. The soft breeze swirling and whistling, a manifestation of wind magic playing around her.

" _I love you… Licth."_

The demon opened his eyes, his gaze focused on the boy's upper chest, where a cross-engraved blue _Maseki_ rested comfortably as a pendant. The soft wind swirled around the boy, the seed of wind magic feeding from the _mana_ around him.

_What a fate…_

Rihito shifted his gaze from Yuno to Asta. He saw the way Asta's emerald eyes lit up and sparked at Yuno's words. He saw his gorgeous brilliant smile, a smile that could eradicate darkness.

That Yuno kid… would be the hardest obstacle for Rihito to possess Asta.

* * *

Today was the day.

Asta had turned fifteen and today was the day he would obtain his _Grimoire_.

Asta was excited and he had walked around and around the clearing since dawn, unable to hold down his impatience, and he couldn't stop himself for telling Rihito all about it.

 **" _Why aren't you with that Yuno kid if you're going to receive Grimoire together then?"_** Rihito asked and Asta made a conflicted expression.

"Yuno has been kind of mean lately. He's in rebellion phase," Asta sighed, rather dispirited. "He's such an awkward guy, you know? And a _tsundere_ ," he continued, feeling fondly exasperated for some unexplainable reason. "He's probably worried sick because I haven't gotten my magic yet."

_Our promise..._

**" _You're still holding onto your denial, I see."_** Rihito wasn't smiling or smirking now, not even remotely amused. He looked kind of irritated, narrowing his blood-red eyes at Asta.

… _I'm not giving it up no matter what._

 **" _You still have to give up sooner or later, you know. Your body is not made to house mana. You have no magic in you."_** Rihito said with flat tone.

"It doesn't matter even though my magic is late to come. I will still find a way to keep our promise no matter what!" Asta clenched his fist and brought it up in front of his face, still holding onto his hope of getting his own magic. He believed it with all of his heart.

…

 **" _Your stupidity never fails to astound me."_** Rihito shook his head, somehow looking exasperated but there was _fondness_ in his tone, which was extremely weird, because he was a demon, and yet he seemed to dote on Asta.

"You just watch. I will get that _Grimoire_!" Asta challenged with a confident grin.

 **" _You don't even need Grimoire if you just say 'yes' to my offer, Asta."_** Rihito reminded him once again of the pact with a whisper, which somehow sounded very loud and prominent with the weight of his gravity. **_"Just say yes, and you can obtain incredible power, more powerful than any magic in this world combined."_**

Rihito's blood-red eyes were shining in the darkness and Asta could feel the pull of desire in his every word.

Asta was wrong before, for treating the offer like Rihito wasn't serious.

The way Rihito spoke now was the evidence of his seriousness. His clawed hands were reaching for Asta. He was about to touch and grab him and Asta knew. He knew despite the years they had known each other, despite Asta considering Rihito as a friend… Rihito was still a _demon_.

Rihito desired a _vassal_. A mortal body to house his demonic soul. He longed for freedom, not stuck in the darkness of the forest under the Three Eyed Demon skull.

Rihito wanted Asta's body to be his sanctuary, so he could be allowed into the light once again.

Asta stepped back, just a hairbreadth away from the claws reach, just until the sunlight separated them from each other. The dark claws vanished when the light touched them and Asta looked at Rihito solemnly.

"I'm sorry, Rihito. I can't accept you in my body," Asta felt regretful because he couldn't help the demon, not at the moment, at least. "But… I will find a way so you can be free."

Rihito froze as he heard that. He looked upward at Asta with widened pupilless eyes.

"I will find a way so even demon can exist in the same light as human." Asta clenched his fists, full of conviction and genuine optimism, and stared at Rihito's shocked blood-red eyes assuredly. "I will _free_ you from the darkness. So just… hang in there, okay?"

Rihito looked speechlessly at him for a full minute before he averted his eyes from Asta's expectant gaze. _**"You should not make promises that you can't keep."**_ The words were bleak, deprecating, but Asta could see that the demon was somehow _moved_. His gaze had softened, and he looked kind of weary rather than upset.

"I'm going to keep my promise no matter what, especially if that promise is a promise with precious friends and family!" Asta grinned widely at the demon and Rihito only shook his head in another exasperated huff.

Well, at least Asta was successful in generating a smile from the demon, not a smirk or a sneer, or a sarcastic laugh, just a small genuine smile.

* * *

" _I always hope that human and elf can coexist peacefully."_

" _I hope someday human and elf can understand each other better."_

" _I hope our love can be the first step to bridge that peace we desperately want, between human race and elf clan."_

Rihito opened his eyes and stared at his sharp demonic claws on his hands.

" _I will find a way so even demon can exist in the same light as human."_

If only all human were like them…

_If only…_

* * *

Rihito felt it before he saw it.

Asta was in danger.

Asta was about to give up.

The moment Asta's spirit broke was the moment Rihito could take over.

But strangely, Rihito didn't want Asta to break.

He wanted Asta to hold on.

He wanted Asta to keep his promise to him.

And Asta never disappointed to surprise him over and over again.

Rihito smiled as part of his real body broke free from the 'seal'.

His _Grimoire_.

No, _Licth's_ cursed _Grimoire_.

This was not a pact between a human and a demon.

The _Grimoire_ chose its Master.

The cursed Five Leafed Clover _Grimoire_ acknowledged Asta's conviction and mental strength. He was worthy of holding the power of a demon despite being only a human child.

The black _Grimoire_ glowed dark red in the darkness for a moment before suddenly vanishing into thin air, probably materializing in front of Asta to give him demonic power.

Rihito grinned in satisfaction. It was his time to walk beside his 'friend' now.

**" _Let's go get them, Asta."_**

Rihito's bat-shaped black wings spread widely and his shadowy mass slowly dissipated and disappeared, leaving only his empty, hard-rock, real form behind in the clearing bellow the Three Eyed Demon Skull.

* * *

Asta called him.

He walked around the clearing and called for Rihito to come out.

Rihito was nowhere to be found.

Asta pulled out his black _Grimoire_ from its pouch. He wanted to ask Rihito if he knew anything about it since he could barely read the spells inside his _Grimoire_.

"I wonder if this Grimoire is _your_ doing…"

Rihito didn't answer him.

* * *

Rihito never showed his presence again in front of Asta.

* * *

Asta met someone that called himself _Licht_ when he was in the middle of a mission to rescue a lot of children who were kidnapped by villains that wanted to drain those children's magic seed from their body, together with Gauche, his senior in his Black Bull Guild and Sister Theresa Rapual, an ex-Magic Knight Captain of the Crimson Lion Guild.

The first line that he said to Asta was, "They hurt my comrade. They got what they deserved," after he stabbed Sister Theresa with his Light Magic, as he revealed himself in the middle of glimmering bright light.

Golden eyes and long white braided hair, floating in the air on a space magic with flowing white robe, holding his defeated and injured comrade, Sally.

Asta met that man once, before, when he was being rescued by the current Wizard King, Julius Novachrono _,_ after Asta was kidnapped by the group of rebels, The Eye of the Midnight Sun.

That beautiful, slender, fair skinned man introduced himself as _Licht,_ the leader of The Eye of the Midnight Sun.

Asta was stunned.

This man… could he be _that demon_?

The way he talked… his mannerism…

Even his silhouette was similar to the shadowy form of Rihito.

However then, Asta realized instantly as he stared into the man's golden eyes.

Despite the similar form, there was no recognition in his eyes when he looked into Asta's.

That man couldn't be Rihito.

* * *

The next time Asta met Rihito again was when he was fighting Ladros, one of Eight Shining Generals from Diamond Kingdom.

This time Asta met Rihito inside himself, as he was about to pass out, and he thought he was dying at the time. Rihito showed up as a large demon in his subconscious plane, and Asta almost couldn't recognize him.

But Rihito's offer still rang true.

 **" _Let me have your body,"_** he said, reaching to grab Asta's body as a whole, but Asta was still Asta after all, and he was as stubborn as a mule, so he dodged.

"Hey, now! What's the big idea?!" Asta yelled at him, surprised and annoyed that he was suddenly attacked like that.

 **" _It's not a bad deal, right? You need the power, don't you? Don't you want to win in this fight against that 'human'?"_** Rihito smirked at him. **_"Leave it to me, I can make that happen instantly."_**

Asta didn't like the malice he felt from Rihito's words and aura.

Before, Asta only felt the 'evil' presence when Rihito awoke from his slumber the first time. Yet, right now…

Right now, Rihito was full of wickedness, his red eyes glinting dangerously and his smirk was full of sharp teeth which seemed ready to _devour_ Asta alive.

Asta didn't like it one bit.

So, Asta fought.

It was true that Asta needed power to defeat Ladros, but he wouldn't let himself be swallowed up by Rihito's consciousness only to get that power.

Asta would borrow Rihito's demonic power, but he would be still in total control of his consciousness and body.

* * *

 ** _"Oh, we're doomed."_ **Rihito said, when Asta's blood, body and consciousness were being swallowed and controlled completely by the Queen of Witches.

"AAAAAH! What do we do?!"

Asta's subconscious could only shriek in horror.

* * *

It was such a relief that Vanessa had everything under control after that.

* * *

Asta was able to _use_ more of Rihito's demonic power by regulating his 'Ki' and using his Demon Slayer sword from his _Grimoire_.

He didn't even need to see Rihito to do that now.

* * *

The selection of Royal Knights had become such a mess because of Langris.

Asta didn't see Rihito, but he felt the same _malice_ of a demon from Langris' Space Attack Magic.

* * *

Asta met the real body of _Licht_ when Royal Knights attacked the main base of The Eye of the Midnight Sun.

It turned quite into a disaster because many of his comrades had turned into other people, _other race,_ to be precise, Elf race.

Those Magic Knights had been forced by forbidden reincarnation ritual into surrendering their bodies so those Elves spirit could awaken. They were forced to betray their friends and kingdom, turning into Elf race with so much _hatred_ and _malice_ , their souls tainted by demonic power that Asta couldn't help thinking if Rihito had anything to do with this.

The demon never spoke to Asta again after that time Asta fought him for control over his demonic power and over his body, but Asta _knew_ he was still lurking inside his subconscious plane, waiting.

Asta didn't know what Rihito was waiting for, but he might have been waiting for _Licht's_ real body to show up.

It was such a luck that even though Yuno had turned into Elf race, he was still Asta's Yuno. He was so glad that Yuno's personality and memories hadn't turned into someone else's despite his appearance.

"There's no force in this universe that can make me forget you, Asta."

Asta was so thankful that he didn't lose Yuno in this devastating fight. He even was excited that he could fight beside Yuno trying to defeat _Licht's_ real body, even though one of Asta's weapon was seized by _Licht_ in the middle, the Demon Dweller one, and how the hell did he use those swords so… so fluidly like that?!

Although, as expected from _Licht's_ real body. Even with all Yuno and Asta's combined power, they couldn't stop _Licht_.

Asta and Yuno were defeated, and Licht and Rhya, along with reincarnated elves went to do the next step of their plan.

At the time, Asta was unconscious, but Rihito didn't try to take over his body.

* * *

Rihito was still inside Asta's subconscious plane.

Who was in _Licht's_ real body then?

* * *

The real Devil… was scary as fuck.

It was such a mess.

Everything was such complicated _cruel_ mess.

Humans… elves… the Devil had manipulated them all.

So many deaths and despair… just because the Devil wanted to walk the mortal plane.

The Devil was from hell.

Rihito wasn't that devil.

Rihito was…

Asta looked at _Licht's_ real body.

Part of the Elves' leader soul was in that body.

The other part was… inside Asta.

It was time to wake him for real then, so he, along with the First Wizard King could finish their business with the Devil.

Asta turned to face Yuno and his most important person looked back at him, nodding, confidence and belief clear in his golden eyes.

"We will defeat the Devil together."

Asta and Yuno, magic and anti-magic, part elf, part demon, part human… their combined power would destroy the Devil and send his remains back to hell.

* * *

The last time he saw Rihito, Asta was asleep and dreaming.

Rihito was still in his demon form.

"Why don't you turn back to the half of your soul?" Asta asked him, confused, and the demon smirked.

 **" _I'm a demon, that place can't accept such vile being as I am,"_** Rihito answered, looking at the blue sky that Asta conjured up inside his dreamscape. **_"This is my punishment for using the forbidden spell, turning myself into a demon."_**

…

"Don't you think… you've punished yourself enough?" Asta inquired tentatively, approaching him rather hesitantly, but he didn't feel any ill intent from the demon, so he got closer and looked upward at the black demonic mass' blood-red eyes. "You deserve rest too." He smiled softly at Rihito and the smirk on his face mellowed slightly into a smile.

 **" _Nah. I'd been sleeping enough to waste four lives time."_** Rihito's bat-wings fluttered and they came up upward, touching Asta's shoulders before enveloping his body unexpectedly. **_"Besides, now that I'm residing in the fifth leaf of your Black Clover Grimoire, I can never leave you. I'm part of your power now, Asta. So… I'll stay by your side until it's time for your mortal life to leave this world."_**

Now, Rihito's smile turned mischievous as he whispered on Asta's left ear and Asta's imaginary bead of sweat just dropped from his temple.

"I'm still not giving you my body!" Asta exclaimed loudly while shoving the demon away from him slightly, yet not unkindly, and Rihito just grinned and laughed at his reaction.

**" _That's quite alright. I'll just stick around until you said 'yes' to me, Asta!"_**

Asta didn't know whether he should be grateful or offended. "Now you're just stubborn. You perfectly know I will never give in." He crossed his arms on his chest. Of course Asta would always chose his humanity, as long as he had Yuno and his friends beside him, he would never turn to the dark side.

**" _Time is all I have now. Besides, nobody knew what will await in the future. You may change your mind someday and… I'm willing to wait until you fulfil your promise to me."_**

Asta widened his eyes slightly as the demon smiled at him softly, he could almost see _Licht's_ gentle expression in his. He showed an expression that _Licht_ had shown when he was reunited once more with the First Wizard King, Lemiel, and when they said good bye to each other.

An expression for a dear friend, the important person in his life.

Asta couldn't help flushing slightly. He didn't know why, but he was happy that the demon thought so highly of him.

"Yeah, alright." Asta gripped his fist tightly in full determination. "I'll try my hardest to fulfill it then, Rihito."

The demon gave him a satisfied huff and nodded before he disappeared.

* * *

When Asta woke up, he realized that he had gotten himself a life-time demonic partner, and had no doubt that he wouldn't have it any other way.

* * *

The aftermath of the fight with the Devil and Elf Clan was unexpected.

Many great obstacles stood in Asta's path to fulfil his dream and promise with Yuno, many adventures awaited in the future, and of course, he was so grateful that his guild mates were standing beside him, and even though he had to part ways with Yuno for a while, he just knew Yuno would wait for him in Clover Kingdom.

The day he departed from the kingdom, Yuno _kidnapped_ him for an hour to talk to him more privately, and he was surprised when Yuno gave him his pendant.

"Yuno…" Asta gaped as he stared at the blue, cross-engraved _Maseki_ in his hand.

"You _must_ come back to me, Asta," Yuno said softly before he acted a little bit out of character by enveloping Asta in a hug, holding him firmly and tightly. "Come back to me, I'll be waiting."

Usually, Yuno would say 'If you can't keep up, I'll leave you,' so it was such a shock that he actually declared that he would wait for Asta to come back to Clover Kingdom before they resumed their rivalry.

Asta couldn't help but hug him back. Yuno was his dear, _dear_ beloved, and even though he would miss him like crazy, he just knew he would always come back to Yuno in the end.

"Silly, of course I'll come back to you," Asta said, almost crying, but he blinked back his tears before he pulled away slightly to look at Yuno in his golden eyes, full of hope and promise. "I'll come back to you and then we will decide who will become the Wizard King!"

Yuno snorted slightly, a confident smirk adorning his face. "That will be me, obviously."

"No freaking way! I'll become the Wizard-king!" Asta protested loudly and stubbornly in reaction and they were back to bicker with each other about it until it was time for Asta to really go (or he would be left behind by his guild) and in a moment of insanity Asta pulled Yuno down to his eye level before smacking a kiss on his mouth to seal the deal.

"Until next time, Yuno!"

Asta laughed mirthfully then, when he loked at Yuno's stunned expression. It was the first time that he witnessed such bewildered look on his beloved rival's face and he couldn't help getting excited until the next time he'd see Yuno again.

_Next time, I'll make him fall head over heels in love with me!_

The indefinite future was such a bright place that was full of hope after all.

* * *

The demon lurking in Asta's subconscious plane slapped his face with his clawed hand.

**" _He is such an untactful brat as always…"_**

But as Rihito thought before, the biggest obstacle to make Asta let go of his humanity was the presence of Yuno… _Licht's Tetia_ in his previous life.

Rihito smirked slightly, feeling challenged.

**" _Now… what should I do to get your heart, Asta?"_**

**END of Vassal**

**Author's Note:**

> This is an open ending, I know. Asta and Yuno aren't exactly together at the end, but it's hopeful alright? And what? I didn't even know at first that Licht really turned himself into a demon using forbidden technique! I swear! And I know there are a lot of spoiler in here (for the anime fan-only), so the warning in that tags above is warranted. Hopefully it was vague enough, so… Also, Licht/Asta is indeed a really rare pairing, so forgive me if this story is plot-heavy instead of fan-service oriented. But as I thought, Yuno/Asta is tsill the best after all *grins excitedly*
> 
> Ahem, so… what do you think? Critiques? Comments? I'll be waiting for your responses as always.


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